The present invention relates to a cam belt, in particular for agricultural machinery.
Conveyor belts which have cam belts as traction means are frequently used, in particular in the field of agriculture. These types of conveyor belts usually have two or more cam belts which run in parallel to one another and are connected to one another by functional elements, for example carriers. On their inner side, the cams belts have evenly interspaced cams which are separated by gaps and which in each case circulate around a driven cam wheel and a carried cam wheel. On their periphery the cam wheels have carrier means spaced apart from one another by a distance that corresponds to the division of the cams. These carrier means engage with gaps in the cam belts which are present between the cams, thus enabling a non-slip drive. The cams belts are generally produced from crosslinked polymer reinforced by fabric plies. Other reinforcement inserts such as cord or steel cable are also known.
DE 10 2007 049 839 B3 describes a rod belt for rod belt conveyors. Two cam belts circulating in parallel to one another and connected to one another by rods extending transversely with respect to the conveying direction are provided as belts. The rods are flattened at their ends, and with these ends rest on the cam belt from above. The rods are fastened to the cam belts by riveting. For this purpose, the cam belts have two punched-out holes situated at a distance from one another, transversely with respect to the conveying direction. Likewise, two holes having the same spacing are provided in the rod ends. For establishing a riveted connection between the rods and the cam belts, the rods are placed on the cam belts in such a way that their holes align with one another. Rivets are then inserted from the underside of the belt, through the aligned holes in the rods and cam belts, with insertion of a large-surface rivet plate in between, and a closing head is produced. The rods are then fixedly connected to the cam belts. The large-surface rivet plate prevents the rivets from being pulled through the cam belt when the riveted connection is being established, or under load during operation.
In the above-described approach, the rivet plates rest centrally on the base of gaps that are formed between the cams. Circulation of the cam belt around a driven cam wheel then results in metal-to-metal contact between the outer surfaces of the carrier means of the cam wheel and the rivet plates. The generally large radial forces on the deflection points and the customary conveying speeds of 0.5 to 8 m/s, as well as the mechanical contact in conjunction with abrasive materials such as soil, dirt, and harvested crop, over the long-term result in a high level of wear on surfaces of the carrier means and of rivet plates which come into contact. This causes a reduction in the reference diameters over time, resulting in increasingly larger differences with respect to the cam division of the cam belt, which adversely affects the intermeshing of the system. In addition, this results in considerable running noise due to the contact between the carrier means of the cam wheels and the rivet plates. If the wear continues until the rivet head is worn down, the functional element detaches from the cam belt, which may result in failure of the entire system.
These disadvantages are avoided with a cam belt that is disclosed in DE 10 2009 036 104 A1. In one embodiment, carrier strips are fixed to the cam belt by screw connections. The screw connections have screw bolts which are centrally vulcanized into a cam of the cam belt. In the process, the heads of the screw bolts are embedded in the cam, and their threaded shanks protrude through a hole in the belt and through a hole in the carrier strips. The carrier strips are fastened to the cam belt by screwing a nut onto the threaded shank of the screw bolt. To be able to absorb the tensile forces which thus act on the head of the screw bolts without damaging the cam belt, in particular to prevent the screw bolt from being pulled through the cam belt, the bolt head rests on a large-surface support element in the form of an anchor plate. It is also known from this publication to weld the screw bolts onto the anchor plate, as the result of which bolt heads may be dispensed with.
That described cam belt of this type operates with low wear and low noise, since the fastening means are vulcanized into a cam. One disadvantage is that vulcanization of the fastening means is relatively complicated.
A cam belt of this type is likewise described in U.S. Pat. No. 4,697,693. For fastening a functional element, such as a carrier strip, to the cam belt, a central through hole is introduced into a cam, and a screw bolt is inserted through the through hole. The carrier strips are fastened to the cam belt by screwing a nut to the threaded shank of the screw bolt. Here as well, the head of the screw bolt rests on an anchor plate to prevent the screw bolt from being pulled through the cam belt. To prevent the head of the screw bolt and the anchor plate from protruding vertically beyond the contour of a customary cam, the height of the cam is correspondingly reduced. The radial extensions of the anchor plate and of the head of the screw bolt are selected in such a way that they are situated within the contour of a customary cam. In this approach, vulcanization of the fastening means into the cam is dispensed with. Here as well, however, metal-to-metal contact between the drive means and the fastening means is not avoided.